Hits such as Peppa Pig can generate additional sales through toys and other products. Photograph: Dean Murray/Rex Features

Animators and computer games developers have urged George Osborne to introduce tax breaks to shore up creative industries that are under pressure, after it emerged he was planning to hand out a 25% tax break for Downton Abbey and other "cinematic" television dramas in next week's budget.

British animation has been in decline in recent years as other countries have offered generous subsidies for cartoonists to move abroad, with Bob the Builder and Thomas the Tank Engine produced in the US and Noddy made in Ireland, and the industry believes the result is British pre-schoolchildren now see largely foreign-made content.

Oli Hyatt, the founder of Blue-Zoo Animation, which helped make Tree Fu Tom on CBeebies, is worried it is easy for ministers to reward drama, after the prime minister visited Washington and dined with President Obama and celebrities including Downton star Hugh Bonneville and Wire actor Idris Elba.

He said: "We believe we have a stronger case, because supporting animation is not just about inward investment but generating intellectual property for the UK – and because young children spend so much time watching our content, possibly over two hours a day."

A tax break on production would cost the Treasury £17m a year, helping support a £300m-a-year industry that employs 4,700 people directly. But the biggest hits, such as Peppa Pig, can generate additional sales through toys and other products of £300m a year – more than a taxpayer-financed film such as the King's Speech.

The computer games industry, which employs 9,000 in Britain, has also long campaigned for tax breaks to match the 20% breaks enjoyed by film, a promise made before the election by the Conservatives, but withdrawn in response to the financial crisis. Games jobs have gone overseas to places such as Montreal, Canada, and British titles like Lara Croft are now developed abroad as the industry tries to trim the £30m to £50m costs of making a big budget game.

Ian Livingstone, the life president of Eidos, the company behind Lara Croft, said he was hopeful that the government would listen this time. "All we want to do is compete on a level playing field with overseas," he added. But government sources said they were not yet certain that the tax break promise made to drama would spread elsewhere..